How can I check my byte flag, verifying that a specific bit is at 1 or 0?

Question

I use a byte to store some flag like 10101010, and I would like to know how to verify that a specific bit is at 1 or 0.

Answer 1

As an extension of @Daoks answer

When doing bit-manipulation it really helps to have a very solid knowledge of bitwise operators.

Also the bitwise "AND" operator in C is &, so what you are wanting to do is:

unsigned char a = 0xAA; // 10101010 in hex
unsigned char b = (1 << bitpos); //Where bitpos is the position you want to check

if(a & b) {
    //bit set
}

else {
    //not set
}

Above I used the bitwise "AND" (& in C) to check whether a particular bit was set or not. I also used two different ways of formulating binary numbers. I highly recommend you check out the Wikipedia link above.